Grandmaster Combat Achievements tasks in Old School Runescape are the ultimate challenge for high-level combat players. These tasks require the highest combat levels, top-tier equipment, and a thorough understanding of boss mechanics to complete successfully. If you're looking to become a master of combat in Old School Runescape, you'll need to complete 129 tasks. These tasks range from killing K'tzitza with a final source of damage being a chin Chomper explosion to killing a corrupted Hunllef with a full set of perfected, corrupted armor equipped. Once you complete all 129 tasks, you will be eligible for the GrandMaster tier. 

In order to become a GrandMaster of combat, you will need to complete all 129 tasks in the master tier. This can be quite difficult, as some of the tasks require precise positioning and knowledge of when to use certain weapons and armor. To help you out, we've compiled a guide on how to complete all 129 tasks in the master tier. 

First, you will need to complete the Baba Bonanza and Lightning Lure tasks. To complete the Baba Bonanza task, you will need to complete 10 Volca kills without dying. For the Lightning Lure task, you will need to complete 15 kills without dying. Both of these tasks can be quite difficult, so it is important to have a good strategy in place. 

Next, you will need to complete the Hydra, Flame Skipper and Multi-Style Specialist tasks. The Hydra task requires you to complete the fight without taking any damage. The Flame Skipper task requires you to complete the fight without using any damage. And the Multi-Style Specialist task requires you to complete the fight with two different styles of combat. 

Once you have completed these three tasks, you will then need to complete the Black Diode Body task. This task requires you to complete the fight with no damage and no healing. 

After you have completed the Black Diode Body task, you will then need to complete the Chompington and Skid tasks. The Chompington task requires you to complete the fight with only melee, while the Skid task requires you to complete the fight with melee in a duo or more. 

Once you have completed these five tasks, you will then need to complete the Dunski and Speed Chaser tasks. The Dunski task requires you to complete the fight with no damage, while the Speed Chaser task requires you to complete the fight as quickly as possible. 

Finally, you will need to complete the GrandMaster tasks. These tasks include the Perfect Maiden, Perfect Bloat, Perfect Nylocass, Perfect Solid Sag, Perfect Zarpus and Perfect Verzik. These tasks are some of the hardest in the master tier, so it is important to have a good strategy in place. 

Once you have completed all 129 tasks in the master tier, you will be eligible for the GrandMaster tier. This tier will give you access to several rewards, including Gomel's Health Five, which can be attached to the Vernic Defender, an antique lamp with 35,000 experience, five daily teleports, two more or wreck like a boss, slayer will now assign you up to 60 boss kills, slayer tasks for Jad and Zuck are increased to two kills per task, the Gold Wars dungeon entrances now only require 25 kill counts, the ecumenical key drop rate is down to one in 45, the coin costs to enter a private instance at God Wars is only 100k OSRS Gold, you can now get the Verzik Slayer Helm, and Gomel's Lucky Penny, which saves charges on weapons and has no use.